The following discussion of the prior art is intended to present the invention in an appropriate technical context and allow its significance to be properly appreciated. Unless clearly indicated to the contrary, however, reference to any prior art in this specification should be construed as an admission that such art is widely known or forms part of common general knowledge in the field.
Pyrrole derivative of present invention is chemically 2-ethoxy-3-(4-(2-(2-methyl-5-(4-(methylthio) phenyl)-1H-pyrrol-1-yl)ethoxy)phenyl)propanoate, which may be optically active or racemic and its pharmaceutically acceptable salts, hydrates, solvates, polymorphs or intermediates thereof. The INN name for pyrrole derivative is Saroglitazar® which is magnesium salt of pyrrole compound of Formula (I), having below chemical structure.

The compound of Formula (I) lower or modulate triglyceride levels and/or cholesterol levels and/or lower density lipoproteins (LDL) and raise HDL plasma levels and hence are useful in combating different medical conditions, where such lowering (and raising) is beneficial. Thus, it could be used in the treatment and/or prophylaxis of obesity, hyperlipidemia, hypercholesteremia, hypertension, atherosclerotic disease events, vascular restenosis, diabetes and many other related conditions. The compound of Formula (I) are useful to prevent or reduce the risk of developing atherosclerosis, which leads to diseases and conditions selected from arteriosclerotic cardiovascular diseases, stroke, coronary heart diseases, cerebrovascular diseases, peripheral vessel diseases and related disorders.
U.S. Pat. No. 6,987,123 B2 (the US '123 patent) discloses novel heterocyclic compounds, their preparation, pharmaceutical compositions containing them and their use in medicine. The US '123 patent discloses five reaction pathways for the synthesis of pyrrole derivatives.
In route-1 the compound of Formula (1a) and (1b) are reacted under Paal-Knoor conditions to obtain compound (1) as shown below:

In route-2 the compound of Formula (1c) and (1d) are reacted in presence of base in suitable organic solvent to obtain the compound (1) as shown below:

In route-3 the compound of Formula (1e) and (1d) are reacted in presence of coupling agents like DCC, EDC etc. to obtain the compound (1) as shown below:

In route-4 the compound of Formula (1f) and (1g) are reacted in presence of rhodium salts such as rhodium (II) acetate in suitable solvents like benzene, toluene, ether, THF, dioxane and the like to obtain the compound (1) as shown below:

In route-5 the compound of Formula (1e) and (1d) are reacted under Wittig Homer conditions to obtain the compound (1) as shown below:

U.S. Pat. Nos. 7,041,837 B2, 7,323,491 B2, 8,110,598 B2, 8,212,057 B2 discloses different pyrrole derivative of Formula (1) and their intermediates.
U.S. PG-Pub. No. 2011/0275669 A1 discloses the process for the preparation of pyrrole derivative of general Formula (1) prepared by the five reaction pathways as disclosed herein above.
International (PCT) publication WO 2012/104869 A1 provides the use of compound of Formula (I) for the treatment of lipodystrophy.
Our own copending application IN 1910/MUM/2013 A discloses substantially amorphous saroglitazar magnesium having percentage crystallinity less than 25% and process for its preparation, which is incorporated herein as reference.
International (PCT) publication WO 2012/104869 A1 provides the use of compound of Formula (1) for the treatment of lipodystrophy.
The different physical properties exhibited by polymorphs affect important pharmaceutical parameters selected from storage, stability, compressibility, density and dissolution rates (important in determining bioavailability). Stability differences may result from changes in chemical reactivity (e.g., differential hydrolysis or oxidation, such that a dosage form discolors more rapidly when comprised of one polymorph than when comprised of another polymorph), mechanical changes (e. g., tablets crumble on storage as a kinetically favored crystalline form converts to thermodynamically more stable crystalline form) or both (e. g., tablets of one polymorph are more susceptible to breakdown at high humidity). Solubility differences between polymorphs may, in extreme situations, result in transitions to crystalline forms that lack potency or are toxic. In addition, the physical properties of the crystalline form to that of an amorphous form may be important in pharmaceutical processing. For example, an amorphous form may provide better bioavailability than the crystalline form. Thus, a pt sent amorphous form may be useful for formulations which can have better stability, solubility, storage, compressibility etc important for formulation and product manufacturing and doesn't degrade to crystalline forms of saroglitazar.
Therefore, it is desirable to have an amorphous form of drugs with high purity to meet the regulatory requirements and also highly reproducible processes for their preparation.
In view of the above, it is therefore, desirable to provide an efficient, more economical, less hazardous and eco-friendly process for the preparation of substantially amorphous saroglitazar. However, the present amorphous form of saroglitazar may provide at least a suitable alternative for development of finished formulations.